0 - The check could not be performed because the second Region could not be mapped into the coordinate system of the first Region.
1 - There is no overlap between the two Regions.
2 - The first Region is completely inside the second Region.
3 - The second Region is completely inside the first Region.
4 - There is partial overlap between the two Regions.
5 - The Regions are identical to within their uncertainties.
6 - The second Region is the exact negation of the first Region to within their uncertainties.
AST A Library for Handling World Coordinate Systems in Astronomy